1. Field of the Invention
The present invention relates to light waveguide telecommunication systems, and is more particularly concerned with structure for providing reconfigurations in a network of light waveguides.
2. Description of the Prior Art
In light waveguide (LWG) telecommunication systems, the task often arises to undertake reconfigurations in a network of light waveguides, for example for the purpose of a standby circuit, a reconnection or for the purpose of an exchange-oriented call set-up or, respectively, cleardown. Electromechanical-optical switches or integrated optical switches can be provided for this purpose; standby circuit measures and reconnections can, in addition, also be effected with the assistance of plug connectors that, however, require a frequently undesirable, direct manipulation. The drive of electromechanical-optical switches or of integrated optical switches as well occurs via corresponding control lines that, however, can quickly prove relatively involved in a branched LWG network having a plurality of decentralized switches.
A switching matrix of mirrors that can be electromechanically switched in position and, therefore, switched on and off, so to speak, is also known for the exchange-oriented structuring of LWG connections between LWG subscriber lines (see VDI Nachrichten, No. 36/7. September 1984, p. 17), whereby control signals output by the calling subscriber via his LWG subscriber line proceed from the switching matrix via small glass strips in the beam path to a selection evaluation device that initiates a control system to actuate a mirror in the path of the appertaining subscriber. Such a mirror matrix which represents a relatively complicated electromechanical structure, however, first of all assumes a concentration of the optical switch elements (mirrors) in precisely this matrix and, secondly, requires an additional matrix or star structure of control lines that lead to the individual mirrors of the matrix.
In a very similar fashion, such a concentration of the optical switch elements in a switching matrix network and a control line structure extending from the offering trunks thereof to a central control device or, respectively, from the latter to the individual switch elements may also be found in another, known optical switching system (see abstract of the Japanese patent 61-164 395).
An optical packet switching system having optical 2.times.2 coupling switches arranged in switching matrix stages is also known from the European patent 0 313 389, whereby each coupling switch comprises two buffer memory devices at its two inputs that lead to the input of an optical switchover device whose two outputs form the two coupling switch outputs, whereby the optical switchover device is preceded in the light waveguide path by an optical demultiplexer with which only light having a wavelength defined individually for a switching matrix stage can be coupled out from a routing header. Proceeding from this demultiplexer, the optical switchover device following in the waveguide path is controlled via an opto-electrical transducer, whereby the optical switchover device proceeds into its one switch condition or into its other switch condition dependent on whether or not light having the wavelength defined for the appertaining switching matrix stage is contained in the routing header. Such a control on the basis of control light individually associated to the switching matrix stages can be practical in a concentrated switching matrix network having relatively few switching matrix stages. If one wished to correspondingly also drive optical switches that are decentrally arranged in the light waveguide network and that can also not be driven switching matrix stage-wise, then this would require a multitude of switch-associated control wavelengths, whereby such a wavelength management, however, cannot be practically realized.
An optical switching system having a multi-stage N.times.N switching matrix network is already known in the art, for example the IEEE Communications Magazine Vol. 25, No. 5, 1987, pp. 50-55, in which the individual optical switching elements are respectively preceded by an optical delay element preceding which a path leading to the optical control element for controlling the appertaining optical switching element branches from the light waveguide. In this switching system, each of the individual useful signal bits to be through connected is respectively coded with its destination address. This, first of all, assumes a corresponding circuit-oriented expense and leads to correspondingly, increased transmission clock rates in the system which, on the other hand, proves inexpedient, particularly when individual bits are not to be respectively through connected in and of themselves but entire messages or when reroutings in the network are only to be undertaken at all at greater time intervals, for example for network reconfiguration in the case of a standby circuit.